1. Field of the Invention
The invention relates to a racket frame, more particularly to a metal racket frame which includes a hollow looped head portion with different outer and inner peripheral wall thicknesses.
2. Description of the Related Art
An ideal racket should be lightweight and is capable of providing a strong return force to a ball struck thereby. The outer appearance and the material of a metal racket frame are usually varied in order to meet these requirements.
FIG. 1 illustrates a conventional metal racket frame which includes a hollow looped head portion 1 that holds a string web 2. When a ball (not strikes the string web 2, the string web 2 applies an inward pulling force (F) on an outer peripheral wall of the head portion 1. The head portion 1 generates a counter force (E) to counteract the pulling force (F). In order to enable the head portion 1 to generate a stronger counter force (E) and further enable the racket to provide a strong return force to the ball which strikes the string web 2, the wall thickness of the head portion 1 is usually increased. An increase in the wall thickness of the head portion 1, however, results in a heavier racket. Such a racket cannot be used in international competitions because of existing weight restrictions for rackets. Furthermore, the use of heavy rackets can result in injuries to beginners.